Deformable member

ABSTRACT

A deformable member can be used in a well tool for use in downhole oil/gas wells. In one embodiment, a deformable member ( 46 ) is described which is deformable between undeformed and deformed positions, and comprises a generally hollow cylindrical body ( 48 ) defining a wall ( 50 ). The wall ( 50 ) includes three circumferential lines of weakness in the form of grooves, with two grooves ( 52, 54 ) provided in an outer surface ( 56 ) of the member wall ( 50 ), and the other groove ( 58 ) provided in an inner surface ( 60 ). The member ( 46 ) is deformed outwardly by folding about the lines of weakness ( 52, 54, 56 ) and is used in particular to obtain sealing contact with a tube in which the member ( 46 ) is located.

RELATED APPLICATIONS

This is a divisional patent application of U.S. patent application Ser.No. 10/336,848, filed Jan. 6, 2003 now U.S. Pat. No. 6,896,049, which isa continuation under 35 USC §120 of PCT/GB01/03072, filed Jul. 9, 2001,which published in English as WO 02/04783 and corresponds to BritishPatent Application GB 0016595.1, filed Jul. 7, 2000 and whose contentsare incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a deformable member. Particularly, butnot exclusively, the present invention relates to a deformable memberfor use in a well tool, especially for providing a metal to metal seal,and to a well tool with a deformable member.

BACKGROUND OF THE INVENTION

It is known to provide metal to metal seals to carry out a wide varietyof sealing operations within tubing such as surface fluid pipe lines andwell tubing of an oil or gas well. Such metal to metal seals arecomplex, expensive to manufacture, must be preformed and often result inpermanent deformation so that the seals cannot be reused. Also, it isknown to provide resilient seals which do not provide metal to metalsealing in such tubing, are cheap and which are reusable, however, suchresilient seals have disadvantages that they do not have the strength ofmetal to metal seals and cannot be used in aggressive environments whichdegrade the seal.

Furthermore, it is known to provide a wide variety of tools for carryingout well operations within tubing of a well, such as an oil or gas well,the tools requiring a seal to enable specific well operations to becarried out. Examples of such tools include tubing hangers, packers,bridge plugs, straddles, gravel-pack packers and the like. Each of suchtools are often complex, including many interrelated parts, and requirecomplex running, support, activating/deactivating and retrieving toolsto achieve sealing and allow the well operation to be carried out usingthe tool. Furthermore, complex operations are often required to beperformed in order to locate, activate/deactivate and/or retrieve thetools.

Similar problems are encountered with tools provided in tubing such asgas or oil pipelines located above ground.

Disadvantages associated with such tools are therefore the relativecomplexity of the tools, the complexity of the operations which arerequired to be carried out in order to locate, activate/deactivateand/or retrieve the tools, and the abovementioned disadvantages ofpresently known seals.

An annular seal is disclosed in U.S. Pat. No. 6,182,755 (Mansure) whichincludes a collapsible bellows. The bellows is expanded for insertiondownhole to reduce its outer diameter and is set by compaction toprovide a seal or anchor. However, the seal of U.S. Pat. No. 6,182,755is not initially rigid, which will create problems during running in andtripping out of a borehole, when the seal is in the expanded position.Also, the bellows itself requires support through support shoulders toprovide an effective seal/anchor; whilst embodiments are disclosedwithout such support shoulders, such would be unlikely to provide aneffective seal/anchor in harsh downhole environments.

SUMMARY OF THE INVENTION

It is amongst the objects of the present invention to obviate ormitigate at least one of the foregoing disadvantages. Embodiments of theinvention may provide an improved seal with the integrity of a metal tometal seal, but which may advantageously be applied to a wide variety ofapplications.

According to a first aspect of the present invention, there is provideda deformable member for use as a seal or anchor, said deformable memberhaving a generally hollow cylindrical body defining a cylinder wallhaving a wall thickness which permits the cylinder wall to deform inresponse to an applied force, to form a ring of material around thecircumference of the cylindrical body, the ring being generallyupstanding from the surface of the cylinder wall.

The ring may be formed on the outer surface of the cylinder wall or theinner surface of the cylinder wall.

Conveniently the applied force is an axial force applied at an end ofthe cylinder. Alternatively the applied force is a radial force.

According to a second aspect of the present invention, there is provideda deformable member having a generally hollow cylindrical body defininga member wall, the wall having at least three circumferential lines ofweakness therein, said lines of weakness being spaced along a main axisof the body, two of said lines of weakness being provided in one of aninner and outer surface of the wall and the other one of said lines ofweakness being provided in the other one of said inner and outersurfaces of the wall, the axially outermost lines of weakness defining azone of deformation of the body, wherein the member is deformable in thedeformation zone in response to an applied force, in a directiontransverse to said body main axis, said direction determined by thelocation of the other one of said lines of weakness in the wall.

Preferably, the applied force is an axial force. Alternatively, theapplied force is a radial force. Preferably also the direction ofdeformation is determined by the location of the other one of said linesof weakness.

In this fashion, a deformable member may be provided, which member isdeformable on application of an axial force thereon. The deformationoccurs in the deformation zone of the member. This provides a widenumber of uses for the deformable member, for example, as a metal tometal seal, and results in the member having a larger, or a smallerdiameter in the zone of deformation. Sealing is achieved by deformationof the member in the deformation zone, to bring the member into contactwith a secondary body with which it is desired to achieve sealingcontact.

Preferably, the deformable member is used in well tools. In thisfashion, the deformable member may form part of a well tool, wherein themember is deformable to carry out a sealing operation. The deformablemember may be carried on a support member of the well tool.

According to a third aspect of the present invention, there is providedthe deformable member of the second aspect of the invention for use in awell tool.

The deformable member may be movable between a substantially undeformedposition and a deformed position. This allows the deformable member tobe run into, for example, well tubing, in a first undeformed positionbefore being forced into a second deformed position to carry out adesired well operation, by application of an axial force. Alternatively,the deformable member may be initially partially deformed or otherwisepreformed into a desired shape, and may be moveable between thepartially deformed or preformed position and a further deformedposition. This may assist in allowing controlling of a desired welloperation, and/or may allow the deformable member to carry out a desiredoperation in both the partially deformed or preformed position and inthe further deformed position.

The deformable member may be carried on a support member of the welltool, and may form part of the well tool itself.

Preferably, the deformable member is locatable in a tube for providingsealing contact with an inner surface of the tube, by outwarddeformation of the deformable member into contact with the tube.Additionally or alternatively, a tube may be located within thedeformable member for sealing contact therewith, by inward deformationof the deformable member into contact with an outer surface of innertube.

Conveniently, the deformable member is of a deformable metal material,for providing metal to metal sealing with the tube, which is also of ametal material. The deformable member may be a carbon steel, stainlesssteel or other suitable non-ferrous alloy. Alternatively, the deformablemember may be a plastics or composite material.

Conveniently, the deformable member is compressible axially to deform.The deformable member may be compressed by a secondary tool coupled tothe deformable member or coupled to a well tool of which the deformablemember may form part. Alternatively, the member may be deformed by anaxial pressure force generated by fluid pressure in a tube in which thedeformable member is located.

The deformable member may be elastically deformable, and may require aretaining force to be exerted thereon, to retain the elasticallydeformed member in a deformed position. After removal of the retainingforce, the member returns to its original shape. Alternatively, theelastically deformable member may be of a pre-formed size which islarger than, and thus interferes with, a mating bore of a secondarybody, such as a tube. Pressing of the seal into the bore may cause anelastic contraction of an outside diameter of the member, resulting inan energizing force, thus removing the need for axial compression toenergize the seal. After removing the member from the bore, the memberreturns to its original size and shape. Preferably, though, thedeformable member is plastically deformable, requiring application of aforce both to move the deformable member between undeformed and deformedpositions. Preferably, the deformable member deforms by folding aboutthe lines of weakness. The deformable member may be moved between adeformed and undeformed position through a number of deformation cycles,allowing multiple uses and reuses of the deformable member.Alternatively, the deformable member may be only once deformable. Thismay allow the deformable member to be used in a “one-shot” operation,for example, for a one-off, permanent or semi-permanent operation.

The lines of weakness may comprise open grooves or channels which closeto allow the member to deform. Each groove or channel may besubstantially V-shaped in cross section, or may be of any alternativecross-section which allows the grooves or channels to easily close.Preferably, the other one of said lines of weakness extends partiallyinto the wall. This advantageously allows the deformable member to bedeformed in the direction transverse to the body main axis in thedesired direction, this direction being determined by the location ofthe axially inner one of said lines of weakness in the inner or outerwall surface, and by this line of weakness extending into the wall, thisline of weakness creating “over-center” stress concentrations inresponse to an axial force. The other one of said lines of weakness maybe disposed in a position between the two axially outer lines ofweakness, with respect to the main axis of the body. Conveniently, thelines of weakness are equidistantly spaced along the wall of the member.

According to a fourth aspect of the present invention, there is provideda deformable metal member for metal to metal sealing with a metal tube,the deformable member comprising a generally hollow cylindrical bodydefining a member wall, the wall having at least three circumferentiallines of weakness therein, said lines of weakness being spaced along amain axis of the body, two of said lines of weakness being provided inone of an inner and outer surface of the wall and the other one of saidlines of weakness being provided in the other one of said inner andouter surfaces of the wall, the axially outermost lines of weaknessdefining a zone of deformation of the body, wherein the member isdeformable in the deformation zone in response to an applied force, in adirection transverse to said body main axis, to bring the member intometal to metal contact with the metal tube and to seal the member to themetal tube, said direction of deformation being determined by thelocation of the other one of said lines of weakness in the wall.

This advantageously allows a deformable metal member to be provided,which member is deformable on application of an applied force intosealing contact with a metal tube. It will be understood that referencesto a “seal”and to “sealing contact”are to contact between the deformablemetal member and the tube which may provide an anchoring of the memberand/or fluid-tight sealing of the member (liquid-tight or gas-tightsealing) with respect to the tube.

Preferably the applied force is an axial force. The two of said lines ofweakness may be provided in the outer surface of the wall to form outerlines and the other one of said lines of weakness may be provided in theinner surface of the wall to form an inner line between the outer lines,such that the deformable member deforms in a direction substantiallyradially outwardly on application of the applied force. This mayadvantageously provide a single circumferential line of contact with atube in which the deformable member is located. Further advantageously,this may present a sharp edge, or slightly radiused circumferential lineof contact with the tube, with a high point-contact load, providing arelatively high, fully circumferential, radially directed force on thetube.

In one embodiment, two of said lines of weakness may be provided in theinner surface of the wall to form inner lines, whilst the other one ofsaid lines of weakness may be provided in the outer surface of the wallto form an outer line of weakness. This advantageously allows thedeformable member to be deformed inwardly for contacting a tube locatedwithin the deformable member.

In further embodiments of the invention, the other one of said lines ofweakness provided in the wall is profiled so that it defines a channelhaving a substantially flat base and inclined side walls, the basehaving a further circumferential groove or channel therein extendinginto the wall. Where the other one of said lines of weakness is an innerline provided in the inner wall surface, this may advantageously resultin the formation of a lip when the deformable member is deformed, thelip being of an outer diameter greater than the major expansion of thedeformable member. It will be understood that references herein to themajor expansion of the deformable member are to the greatest outerdiameter of a main part of the deformable member in the region of thedeformation zone, when the deformable member is deformed. The lip mayadvantageously be easily deformable to deform into an ovalised ordamaged tube or other bore, and may further advantageously provide a lowactuating energy seal for use in low pressure environments, and/or toprovide a gas-tight seal with a tube or bore.

In an alternative embodiment, the substantially flat base of the otherone of said lines of weakness in the wall includes two substantiallyV-shaped channels or grooves connected by a portion of the wall which iscurved in cross-section, to provide a rounded lip when the deformablemember is deformed.

In a still further alternative embodiment, the deformable member mayfurther comprise a circumferential, substantially upstanding rib on asurface of the wall, the rib being disposed on the opposite side of themember and wall from the inner line of weakness, which rib engages intoa wall of a tube on deformation of the deformable member. Preferably,there are two ribs provided on the outer surface of the wall, the ribstapering outwardly from the surface and being adapted to engage into atube in which the deformable member is located. Conveniently, each ribis substantially V-shaped in cross-section, and the ribs are axiallyspaced along the wall on either side of the part of the wall in whichthe other one of said lines of weakness is located, and inclined towardone another. Advantageously, this may cause the ribs to engage in thewall of the tube when the deformable member is deformed such thatapplication of further axial force on the deformable member causes theribs to further engage into the tube wall, further improving engagement.

In a yet further alternative embodiment, the other one of said lines ofweakness may be located in the member wall axially closer to one of thetwo of said lines of weakness, such that the deformable member deformsnon-symmetrically about the other one of said lines of weakness. Thus,advantageously, when the deformable member is in a deformed position,application of, for example, fluid pressure loading on the deformablemember may exert a biased energizing load upon the deformable member.

In a still further alternative embodiment, there are four lines ofweakness, two of said lines of weakness being provided in one of theinner and outer surfaces of the wall forming axially outer lines ofweakness, and the other two of said lines of weakness provided in theother one of the inner and outer surfaces of the wall forming axiallyinner lines of weakness, to create a flat portion between the axiallyinner lines of weakness in one of the inner and outer wall surfaces. Theaxially inner lines of weakness determine the direction of deformationof the deformable member and may be provided in the inner surface of thewall. The flat portion defined between the two axially inner lines ofweakness may carry ridges for engaging a tube in which the deformablemember is located, when the member is deformed. The ridges may becircumferentially extending ridges, screw threads or the like. This mayadvantageously allow the deformable member to act as both an anchorwithin a tube and/or as a seal.

In further alternative embodiments, the outer surface of the flatportion defined between the two inner lines of weakness may be laminatedwith a sealing material which provides sealing with a tube in which thedeformable member is located. The sealing material may be a plastics orelastomeric material such as Nitrile, Viton, Teflon (Trade Marks) or arelatively soft metal material. This may advantageously provide a sealunder a low applied force, to allow gas-tight sealing to be achievedrelatively easily.

In a yet further alternative embodiment, the outer surface of the flatportion defined between the two axially inner lines of weakness mayinclude a circumferential groove in which a seal may be located. Theseal may be of a plastics or elastomeric material.

In a still further alternative embodiment, there may be four lines ofweakness, provided alternately along the body in the outer and innersurfaces of the wall. This allows the deformable member to besimultaneously deformed outwardly and inwardly. The deformable membermay therefore be deformed into engagement with both a tube in which thedeformable member is located, and an inner tube located within thedeformable member.

In yet further alternative embodiments, there may be at least five linesof weakness, three of said lines of weakness provided in one of theinner and outer surfaces of the wall, and the other two of said lines ofweakness provided in the other one of the inner and outer surfaces ofthe wall. This creates a deformation zone between the axially outermostlines of weakness with folding deformation occurring between theoutermost lines to create multiple circumferential lines of contact withone of a tube in which the deformable member is located and a tubelocated in the deformable member, whilst providing singlecircumferential line contact with the other one of the external andinternal tubes. In a preferred such embodiment, the three ones of saidlines of weakness are provided in the outer surface of the wall and formouter lines, whilst the other two ones of said lines of weakness areprovided in the inner surface of the wall and form inner lines. This mayprovide double circumferential lines of contact with a tube in which thedeformable member is located, and a single circumferential line ofcontact with a tube located in the deformable member. In furtheralternatives, there may be a plurality of lines of weakness.

The deformable member may further comprise a deformation aid to aiddeformation of the member in response to the applied force. Thedeformation aid may comprise an elastomeric element such as an O-ring orpreformed plastics or rubber insert. In one embodiment, the deformationaid may be provided in the generally hollow cylindrical body. This isparticularly advantageous in that during deformation of the member, theaid may simply fill a void around which deformation of the member maytake place. Alternatively, the deformation aid may comprise a garterspring.

In a still further alternative embodiment, the deformable member mayserve as an anti-extrusion seal, to prevent extrusion of a secondaryexpandable seal. Such expandable seals may comprise expandable rubber orplastics based elements. Conventionally, such seals are carried by acarrier mandrel or the like. High differential pressures across the sealthrough an annulus defined between the mandrel and the bore of a tube inwhich it is located can cause seal extrusion, due to the low strength ofthe seal element material. Conventional anti-extrusion rings areprovided in an attempt to prevent this, however, these do not expand tomeet the seal bore, leaving a significant annular gap. The deformablemember may be deformable into contact with the bore to close the annulargap and prevent extrusion of the seal. There may be provided twodeformable members for surrounding the seal, to close the annular gapand seal the seal to the bore.

In an again further alternative embodiment, a collapse aid may beprovided, serving to assist in moving the deformable member from adeformed position to an undeformed position. The collapse aid may be asleeve adapted to be located around the deformable member and to abutthe deformable member in the deformation zone, when the member is in adeformed position. This may advantageously allow a force to be exertedon the member to assist in moving it to an undeformed position. Thus, adirect and controlled recovery of the deformable member to an undeformedposition may be possible without requiring application of a relativelyhigh tensile loading upon the member. Recovery may be achieved by acombination of application of an axial tensile load and a force exertedby the collapse aid. This may be particularly of use in situationswhere, for example, high stresses involved in deforming the member causepermanent damage, making it difficult to retract the member with apurely axial tensile load thereon.

According to a fifth aspect of the present invention, there is provideda deformable member, the member comprising a body having a first,generally hollow cylindrical body portion of a first general wallthickness, and a second, hollow bulbous deformable body portion, atleast part of the second, deformable body portion being of a wallthickness less than said first wall thickness of the first body portion,the second, deformable body portion being deformable in response to anapplied force, in a direction transverse to a main axis of the body, toallow the member to deform.

According to a sixth aspect of the present invention, there is providedthe deformable member of the fifth aspect for use in a well tool.

Preferably, the second, hollow bulbous deformable body portion has amaximum outside diameter greater than that of the first, generallyhollow cylindrical body portion. This allows the deformable member to bedeformed outwardly into contact with a tube in which the deformablemember is located, to provide a soft, rounded contact with the tubewall.

Advantageously, this provides a progressive, distributed load over arelatively large surface contact area with the tube wall, avoiding highstress concentration nodes. This may be particularly suited to cyclicmultiple deformation applications. Alternatively, the second, hollowbulbous deformable body portion may extend inwardly to engage a tubinglocated within the deformable member.

According to a seventh aspect of the present invention, there isprovided a deformable member, the member comprising a body having afirst, generally hollow cylindrical body portion of a first general wallthickness, and a second, hollow deformable body portion, at least partof the second, deformable body portion being of a wall thickness lessthan said first wall thickness of the first body portion, the second,deformable body portion being deformable in response to an appliedforce, in a direction transverse to a main axis of the body, to allowthe member to deform.

According to an eighth aspect of the present invention, there isprovided the deformable member of the seventh aspect for use in a welltool.

The first, generally hollow body portion may include a first part of thewall of the member body, and may define circumferentially extendingshoulders for supporting and transferring force to the second, hollowdeformable body portion.

The second hollow deformable body portion may include a second part ofthe wall of the member body. The second part of the wall may be definedbetween two circumferentially extending lines of weakness formed in oneof an inner and outer surface of the member wall.

According to a ninth aspect of the present invention, there is provideda bridge plug for location in well tubing of a well borehole, forselectively sealing an annulus defined between the well tubing and thebridge plug from an internal bore of the bridge plug following settingof the bridge plug in the well tubing, the bridge plug including adeformable seal having a generally hollow cylindrical body defining aseal wall, the wall having at least three circumferential lines ofweakness therein, said lines of weakness being spaced along a main axisof the body, two of said lines of weakness being provided in one of aninner and outer surface of the wall and the other one of said lines ofweakness being provided in the other one of said inner and outersurfaces of the wall, the axially outermost lines of weakness defining azone of deformation of the body, wherein the seal is deformable in thedeformation zone in response to an applied force applied followingsetting of the bridge plug, in a direction transverse to said body mainaxis, said direction determined by the location of the other one of saidlines of weakness in the wall.

This advantageously provides a bridge plug which can be run-in to welltubing in a running position, with a deformable seal of the bridge plugin an undeformed position. The bridge plug may then be set at a desiredlocation within the well tubing and the seal deformed into engagementwith the well tubing by applying a compressive load thereon.

Also advantageously, the bridge plug is actuateable to an unset positionby applying an axial tensile load to the seal member so that thedeformable seal is moved to the undeformed position and the bridge plugsubsequently removed from the well.

Additional and/or alternative features of the deformable seal aredefined above with reference to the deformable member of the first tothird aspects of the present invention.

According to a tenth aspect of the present invention, there is providedabridge plug for location in well tubing of a well borehole, forselectively sealing an annulus defined between the well tubing and thebridge plug from an internal bore of the bridge plug following settingof the bridge plug in the well tubing, the bridge plug including adeformable seal in the form of a deformable member as defined in any oneof the first to sixth aspects of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a number of interrelated welltools, each incorporating a deformable member in accordance with thepresent invention;

FIGS. 2A and 2C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a firstembodiment of the present invention, shown in an undeformed position;

FIG. 2B is an enlarged view of part of the deformable member shown inFIG. 2A;

FIGS. 3A and 3C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 2A to 2C, shown in adeformed position;

FIG. 3B is an enlarged view of part of the deformable member shown inFIG. 2A;

FIGS. 4A and 4B are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a secondembodiment of the present invention, shown in an undeformed position;

FIGS. 5A and 5B are longitudinal sectional views of the deformablemember of FIGS. 4A and 4B, shown in a deformed position;

FIG. 5C is a longitudinally sectioned perspective view of the deformablemember shown in FIG. 5B;

FIGS. 6A and 6C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a thirdembodiment of the present invention, shown in an undeformed position;

FIG. 6B is an enlarged view of part of the deformable member shown inFIG. 6A;

FIGS. 7A and 7C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 6A to 6C, shown in adeformed position;

FIG. 7B is an enlarged view of part of the deformable member shown inFIG. 7A;

FIG. 7D is a longitudinally sectioned perspective view of the deformablemember shown in FIG. 7C;

FIGS. 8A and 8C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a fourthembodiment of the present invention, shown in an undeformed position;

FIG. 8B is an enlarged view of part of the deformable member shown inFIG. 8A;

FIGS. 9A and 9C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 8A to 8C, shown in adeformed position;

FIG. 9B is an enlarged view of part of the deformable member shown inFIG. 9A;

FIGS. 10A and 10C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a fifthembodiment of the present invention, shown in an undeformed position;

FIG. 10B is an enlarged view of part of the deformable member shown inFIG. 10A;

FIGS. 11A and 11C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 10A to 10C, shown in adeformed position;

FIG. 11B is an enlarged view of part of the deformable member shown inFIG. 11A;

FIGS. 12A and 12C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a sixthembodiment of the present invention, shown in an undeformed position;

FIG. 12B is an enlarged view of part of the deformable member shown inFIG. 12A;

FIGS. 13A and 13C are longitudinal sectional and perspective views,respectively, of the deformable member shown in FIGS. 12A to 12C, shownin a deformed position;

FIG. 13B is an enlarged view of part of the deformable member shown inFIG. 13A;

FIGS. 14A and 14C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a seventhembodiment of the present invention, shown in an undeformed position;

FIG. 14B is an enlarged view of part of the deformable member shown inFIG. 14A;

FIGS. 15A and 15C are longitudinal sectional and perspective views,respectively, of the deformable member shown in FIGS. 14A to 14C, shownin a deformed position;

FIG. 15B is an enlarged view of part of the deformable member shown inFIG. 15A;

FIGS. 16A and 16C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with an eightembodiment of the present invention, shown in an undeformed position;

FIG. 16B is an enlarged view of part of the deformable member shown inFIG. 16A;

FIGS. 17A and 17C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 16A to 16C, shown in adeformed position;

FIG. 17B is an enlarged view of part of the deformable member shown inFIG. 17A;

FIGS. 18A and 18C are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a ninthembodiment of the present invention, shown in an undeformed position;

FIG. 18B is an enlarged view of part of the deformable member shown inFIG. 18A;

FIGS. 19A and 19C are longitudinal sectional and perspective views,respectively, of the deformable member shown in FIGS. 18A to 18C, shownin a deformed position;

FIG. 19B is an enlarged view of part of the deformable member shown inFIG. 19A;

FIGS. 20A and 20B are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a tenthembodiment of the present invention, shown in an undeformed position;

FIGS. 21A and 21C are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 20A and 20B, shown in adeformed position;

FIG. 21B is an enlarged view of part of the deformable member shown inFIG. 21A;

FIG. 21D is a longitudinally sectioned perspective view of thedeformable member shown in FIG. 21C;

FIGS. 22A and 22B are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with an eleventhembodiment of the present invention, shown in an undeformed position;

FIG. 22C is a longitudinally sectioned perspective view of thedeformable member shown in FIG. 22B;

FIGS. 23A and 23C are longitudinal sectional and perspective views,respectively, of the deformable member shown in FIGS. 22A to 22C, shownin a deformed position;

FIG. 23B is an enlarged view of part of the deformable member shown inFIG. 23A;

FIG. 23D is a longitudinally sectioned perspective view of thedeformable member shown in FIG. 23C;

FIGS. 24A and 24C are front and perspective views, respectively, of adeformable member in accordance with a twelfth embodiment of the presentinvention, shown in an undeformed position;

FIG. 24B is an enlarged view of part of the deformable member shown inFIG. 24A;

FIGS. 25A and 25C are front and perspective views, respectively, of thedeformable member shown in FIGS. 24A to 24C, shown in a deformedposition;

FIG. 25B is an enlarged view of part of the deformable member shown inFIG. 25A;

FIGS. 26A and 26B are longitudinal sectional and longitudinallysectioned perspective views, respectively, of a deformable member inaccordance with a thirteenth embodiment of the present invention, shownin an undeformed position;

FIGS. 27A and 27B are longitudinal sectional and longitudinallysectioned perspective views, respectively, of the deformable membershown in FIGS. 26A and 26B, shown in a deformed position;

FIG. 27C is an enlarged view of part of the deformable member shown inFIG. 27A;

FIGS. 28A and 28C are longitudinal sectional and longitudinallysectioned perspective views, respectively, of a deformable member inaccordance with a fourteenth embodiment of the present invention, shownin an undeformed position;

FIG. 28B is an enlarged view of part of the deformable member shown inFIG. 28A;

FIGS. 29A and 29C are longitudinal sectional and longitudinallysectioned perspective views, respectively, of the deformable membershown in FIGS. 28A and 28B, shown in a deformed position;

FIG. 29B is an enlarged view of part of the deformable member shown inFIG. 29A;

FIG. 30 is a view of the member of FIG. 28A, shown mounted on a mandreland in the deformed position of FIG. 29A, where it has been deformedinto contact with a tube in which the member is located;

FIG. 31 is a view similar to that of FIG. 30, with the mandrel shownincluding a pressure vent port;

FIG. 32 is a view similar to that of FIG. 30, showing a deformablemember similar to that of FIG. 28A, except including a pressure ventport and being sealed to the mandrel by a single seal;

FIGS. 33A and 33B are longitudinal sectional and longitudinallysectioned perspective views, respectively, of a deformable member inaccordance with a fifteenth embodiment of the present invention, shownin an undeformed position, and including a deformation aid;

FIGS. 34A and 34B are longitudinal sectional and longitudinallysectioned perspective views, respectively, of the deformable membershown in FIGS. 33A and 33B, shown in a deformed position;

FIG. 34C is an enlarged view of part of the deformable member shown inFIG. 34A;

FIGS. 35A and 35B are views of deformable members acting asanti-extrusion seals for preventing extrusion of a conventional seal,FIG. 35A showing the members in an undeformed position, and FIG. 35Bshowing the members in a deformed position in location in a tube,respectively;

FIGS. 36A and 36B are schematic views of the member of FIG. 2A and acollapse aid for aiding movement of the member to an undeformedposition, the member shown deformed in FIG. 36A and undeformed in FIG.36B, respectively;

FIGS. 37A and 37B are longitudinally sectioned perspective andlongitudinal sectional views, respectively, of a first embodiment of abridge plug incorporating a deformable seal, in accordance with thepresent invention, the bridge plug shown in a running position where thedeformable member is in an undeformed position;

FIGS. 38A and 38B are enlarged views of the bridge plug shown in FIG.37B, showing upper and lower ends respectively of the bridge plug;

FIGS. 39A and 39B are enlarged views of a ratchet mechanism of thebridge plug shown in FIG. 37B, and a perspective view of segments of theratchet mechanism, respectively;

FIG. 40 is an enlarged view of the deformable member of the bridge plugshown in FIG. 37B;

FIGS. 41A and 41B are exploded perspective and perspective views,respectively, of a slip mechanism forming part of the bridge plug shownin FIG. 37A;

FIG. 42 is an enlarged view of a connecting lower end of the bridge plugshown in FIG. 37B;

FIGS. 43A and 43B are views, similar to the views of FIGS. 37A and 37B,of the bridge plug in a set position, where the deformable member is ina deformed position;

FIG. 44 is an enlarged view of the deformable member of the bridge plugin the deformed position shown in FIG. 43B;

FIGS. 45A and 45B are exploded perspective and perspective viewsrespectively of the slip mechanism of the bridge plug shown in a setposition, when the bridge plug is in the set position shown in FIG. 43A;

FIGS. 46A and 47A are views, similar to the views of FIGS. 37A and 37B,of the bridge plug when it has been returned to an unset position, withthe deformable member in the undeformed position, after having been setas shown in FIGS. 43A and 43B;

FIGS. 46B and 47B are enlarged views of the ratchet mechanism of thebridge plug in the unset position of FIGS. 46A and 47A, respectively,

FIGS. 48A and 48B are longitudinally sectioned perspective andlongitudinal sectional views, respectively, of a second embodiment of abridge plug incorporating a deformable seal, in accordance with thepresent invention, the bridge plug shown in a running position, similarto that of the bridge plug shown in FIGS. 37A and 37B, where thedeformable member is in an undeformed position;

FIGS. 48C and 48D are enlarged views of the bridge plug shown in FIG.48B, showing upper and lower ends respectively of the bridge plug;

FIGS. 49A and 49B are enlarged views of a locking key mechanism formingpart of the bridge plug shown in FIGS. 48A and 48B, respectively,

FIGS. 49C, 49D and 49E are enlarged views of a slip mechanism, aretractable ratchet mechanism, and a transfer key mechanism,respectively, all forming part of the bridge plug shown in FIG. 48A;

FIG. 50A is a view of the bridge plug shown in FIG. 48B, with part ofthe bridge plug removed, for clarity;

FIGS. 50B and 50C are exploded perspective and an enlarged view,respectively, of the retractable ratchet mechanism shown in FIG. 48A,with part of the bridge plug removed for clarity;

FIGS. 50D and 50E are exploded perspective and an enlarged view,respectively, of the transfer key mechanism shown in FIG. 48A, with partof the bridge plug removed for clarity;

FIGS. 51A and 51B are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a furtherembodiment of the present invention, shown in an undeformed position;

FIGS. 52A and 52B are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 51A and 51B, shown in adeformed position;

FIGS. 53A and 53B are longitudinal sectional and perspective views,respectively, of a deformable member in accordance with a still furtherembodiment of the present invention, shown in an undeformed position;

FIGS. 54A and 54B are longitudinal sectional and perspective views,respectively, of the deformable member of FIGS. 53A and 53B, shown in adeformed position; and

FIG. 55 is a graphical representation of test results for a load vs.deformation test on a typical deformable member of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring firstly to FIG. 1, there is shown a schematic illustration ofa number of interrelated well tools, each incorporating a deformablemember (not shown in FIG. 1) in accordance with the present invention.

In FIG. 1, a well assembly indicated generally by reference numeral 10is shown, located in a borehole 12 of an oil well. An upper portion ofthe borehole 12 is lined with steel casing 14 in a fashion known in theart. The well assembly 10 extends into the borehole 12 from surface, andincludes a number of well tools, provided for carrying out a variety ofwell operations. Each of these well tools are in themselves well knownin the art. However, each of the tools includes a deformable member inaccordance with the present invention, which provides a sealing and/oranchoring function for each tool. Embodiments of such deformable membersare shown in FIGS. 2A to 36B, and will be described in more detailbelow. However, generally speaking, each of the deformable membersprovides sealing and/or anchoring engagement with a tube in which thedeformable member is located, and/or a tube located within thedeformable member, to allow the well function to be carried out.

Typical tools shown in FIG. 1 and including a deformable member are awireline stuffing box/coiled tubing injector head 16; a lubricator quickconnect 18; a drilling Blow Out Preventer (BOP) 20; a wellhead, tree ortubing hanger 22; a bridge plug 24 (embodiments of which will bedescribed in detail below with reference to FIGS. 26A to 39E); aretrofit plug 26 for engaging nipples; a packer 28; variable annularexternal and internal venturis 30,32; a lateral borehole window 34; aPolished Bore Receptacle (PBR) 36; a liner hanger 38; a straddle 40,such as a high expansion straddle; an External Casing Packer (ECP) 42;and a gravel pack packer 44. Further uses are as part of highpressure/high temperature packers; high pressure/high temperature bridgeplugs; liner hangers/liner laps; stackable straddles; selective monoborelock mandrels; high pressure/high temperature tool body seals (toBritish Standard 200 series O-ring size); tubing expansion joints; PBRstabs; horizontal tree plugs; sliding sleeves; true metal to metal (MTM)barrier valves (large bore); wireline stuffing boxes; and lubricatorconnectors. In particular, the deformable member has uses where MTMsealing/anchoring is required.

These and other uses of the deformable member will be discussed withreference to particular embodiments of the invention shown in FIGS. 2Ato 25C and discussed below.

FIGS. 2A to 29C; 33A to 34C; and 51A to 54B show various longitudinalsectional, enlarged sectional, perspective and longitudinally sectionedperspective views of deformable members in accordance with variousembodiments of the present invention, as described above, in undeformedand deformed positions.

Turning initially to FIGS. 2A to 3C, there is shown a deformable memberindicated generally by reference numeral 46, in accordance with a firstembodiment of the present invention. The deformable member 46 is shownin FIGS. 2A to 2C in an undeformed position, and comprises a generallyhollow cylindrical body 48 defining a wall 50 of the member 46. The wall50 includes three circumferential lines of weakness in the form ofgrooves, spaced equidistantly along the wall 50, with two grooves 52 and54 provided in an outer surface 56 of the member wall 50, and the othergroove 58 provided in an inner surface 60 of the member wall 50. Each ofthe grooves 52,54 and 58 are substantially V-shaped in cross-section andare formed in the deformable member by a finishing process such as amilling or turning operation.

The deformable member 46 is hollow to allow the member to be located ona supporting member such as an inner mandrel or sleeve (not shown), toform part of a well tool or the like for running the deformable memberinto the borehole 12 of FIG. 1.

FIG. 2B is an enlarged view of part of the member wall 50 of thedeformable member 46 shown in FIG. 2A, and shows the grooves 52,54 and58 in more detail. The axially outermost grooves 52 and 54 define a zoneof deformation 62 of the deformable member 46, shown in FIG. 2A and, aswill be described with reference to FIGS. 3A to 3C, deformation of thedeformable member 46 is restricted to the deformation zone 62.

The two grooves 52 and 54 in the outer surface 56 of the member wall 50extend into the wall 50 to a depth approximately equal to half the wallthickness. The other groove 58 in the inner surface 60, however, extendsto a greater depth within the member wall 50 and, as shown in FIG. 2B,ideally extends to a depth greater than half the wall thickness of themember wall 50.

Turning now to FIGS. 3A to 3C, the deformable member 46 is shown in thedeformed position. The member 46 is deformed in one of a number offashions. Generally speaking, there are four generic energizingprinciples for deforming the member 46. These are the application of anaxial force; the application of an axial force with spring assist;differential piston area; and relative degrees of freedom. Of course, acombination of such principles may be employed for deforming the member46, and such principles apply for each of the deformable membersdiscussed herein.

Considering axial loading, in this case, the member 46 is deformed byapplication of an axial force in the direction of the arrows A shown inFIG. 3A. To allow the deformable member 46 to deform, the member isconstructed from a tough, malleable material which allows the member 46to deform in the deformation zone 62. Typical suitable materials may becarbon steel, stainless steel or other malleable non-ferrous alloys.However, it will be understood that any other material having suitablematerial properties, such as a plastics material, may be selected.

The axial force is exerted upon the member 46 by a setting tool (notshown), and application of the axial force in the direction of thearrows A causes the member 46 to fold by deforming in the deformationzone 62, such that the member wall 50 deforms outwardly.

This deformation is achieved by causing the grooves 52,54 and 58 toclose on application of the axial force, as shown particularly in FIG.3B, which is an enlarged view of the member wall 50 in the deformedposition. When deformed, the member 46 “bulges” outwardly to engage atube (not shown) in which the deformable member is located. Thus thecompressive axial loading on the member 46 forces the expanding portionin the deformation zone 62 into contact with a mating part of the tube.This load must be sustained or otherwise retained to ensure continuousenergizing of the member 46 in the deformed position. The expandedportion thus forms a contact with the mating part of the tube to providea seal. A conventional type seal such as an O-ring or T-seal (not shown)is used to seal the non-expanding portion of the member 46 outside thedeformation zone 62 to the mandrel, as will be described below.

The outer diameter of the member 46 in the region of the deformationzone 62 is determined by the axial distance between the groove 58 in theinner member wall surface 60 and the adjacent grooves 52 and 54 in theouter member wall surface 56. The member 46 is arranged to deform in anoutward direction as shown in FIG. 3A by the location and depth of thegroove 58, which extends into the member wall 50 to a greater depth thaneither of the grooves 52 or 54. It will be understood that this createsa high stress concentration at a tip 64 of the groove 58 when the axialforce is applied, causing the member 46 to fold and deform outwardly.This forms a circumferential edge 66 shown in FIG. 3C, which provides asharp, circumferential point load with a tube (not shown) such as aborehole casing in which the member 46 is located, to provide a highload radial force and create a good seal between the member 46 and thetube.

When it is desired to return the member 46 to the undeformed position ofFIG. 2A, it is necessary only to apply an axial force to the member 46in the opposite direction to the arrows A of FIG. 3A. This extends themember 46 and causes the member wall 50 in the region of the deformationzone 62 to return to the undeformed position of FIG. 2A. It will beappreciated by persons skilled in the art that, depending upon theselection of the material for the deformable member 46, the member maybe either plastically or elastically deformable. Where the member 46 isplastically deformable, the member will remain in a deformed orundeformed position until a force is applied to the member to move it tothe other position.

Where the member 46 is elastically deformable, the member will beresilient and will tend to return to either a deformed or undeformedposition in the absence of an activating force retaining the member inthe desired position.

The spring assisted energizing principle functions in conjunction withthe application of an axial load as discussed above. A spring (notshown) is provided, typically a compression type spring, located in linewith the direction of the applied axial load, in the direction of thearrows A of FIG. 3A. This is beneficial both in preventing de-energizingthrough a backlash and in preventing de-energizing due to creep. In thecase of preventing de-energizing through backlash, the inclusion of sucha spring allows the axial loading on the member 46 to remain relativelyconstant in the event that any mechanical backlash is present in aload-locking system, such as a ratchet provided on a bridge plug, aswill be described in more detail below. In the case of preventingde-energizing due to creep, it is considered possible that the member 46will be subject to additional deformation under the influence of thefailure mechanism known as “creep”. In the event of this occurring, anyloss of energizing load experienced due to, for example, shortening ofthe member 46, will be compensated for by the spring.

The differential piston area and degree of freedom energizing principleswill be discussed in more detail with reference to FIGS. 30 to 32 below.

The deformable member 46 shown in FIGS. 2A to 3C has particularapplications in downhole well assemblies as a static seal; to provideflow control for a borehole or tubing; and in non-flow typeapplications.

As a static seal, the deformable member 46 may be provided as part of abridge plug, such as the bridge plug 24 of FIG. 1 (as will be describedin more detail with reference to FIGS. 37A to 50E below), a packer suchas the packer 28, an ECP such as the ECP 42, as well as in tool bodyconnections and pipeline/flow line connections.

To provide flow control, the deformable member 46 may be provided aspart of a variable annular venturi, such as the venturis 30 and 32 (FIG.1), which provide flow control in an annular flow area defined between atube in which the member 46 is located and the tool and string to whichthe member 46 is connected. When the member 46 is in the undeformedposition, fluid flow occurs through a full annular flow area; partialdeformation to a position between the undeformed position of FIG. 2A andthe deformed position of FIG. 3A causes a partial restriction of theflow area, whereas full deformation of the member 46 to the positionshown in FIG. 3A causes full closure of the annular flow area. Furtherflow control applications are as an alternate sliding side door, whichoperates in a similar fashion to the venturi 30,32, with the member 46provided within a self-contained ported annular housing (not shown). Themember 46 is deformed between the undeformed and deformed positions toprovide on/off control of flow from tubing coupled to the member 46 toan external annulus, and vice-versa.

Non-flow applications of the deformable member 46 include as a wirelinesidewall cutter incorporating the deformable member 46. In this case,the member 46 is provided as part of a tool located in a casing,together with a wireline located externally of the member 46, in anannulus defined between the casing wall and the member 46. Deformationof the member 46 to the deformed position of FIG. 3A causes the wirelineto be crimped or cut against the wall of the tube. Equally, the member46 can be provided within a casing to act as a tubing cutter or crimper.The high circumferential point load obtained through contact between thecircumferential edge 66 of the member 46 and a tube acts to crimp or cutthe tube when the point load exceeds the yield point of the tubematerial.

In a similar fashion, the member 46 can be provided as part of a toolfor obtaining electrical connection through, for example, a plasticsmembrane lined tube, wherein, upon deformation of the member 46 to thedeformed position, the plastics membrane is perforated, to obtain metalto metal electrical connection through the membrane, between the member46 and the tube.

Finally, the member 46 can be used as part of a casing scraper tool,deformed into light contact with, for example, a casing wall. The member46 is then reciprocated within the casing to remove debris from thecasing wall. In a similar fashion, the member 46 can be provided as partof a debris barrier/junk catcher tool, where the member 46 is deformedinto light contact with the casing wall. This provides a barrier againstthe passage of debris into the casing below the member.

As discussed above, FIGS. 4A to 25C; 33A to 34C and 51A to 54B disclosedeformable members in accordance with alternative embodiments of thepresent invention, similar to the deformable member 46 of FIGS. 2A to3C. For clarity, only the differences between the deformable members ofFIGS. 4A to 25C and 33A to 34C relative to the deformable member 46 ofFIGS. 2A to 3C will be discussed herein. Like components of thedeformable members of FIGS. 4A to 25C with the deformable member 46 andsubsequent embodiments share the same reference numerals, with theaddition of the letters “a”, “b”, “c” etc, for each new embodiment.

FIGS. 4A to 5C show a deformable member indicated generally by referencenumeral 46 a, in accordance with a second embodiment of the presentinvention. The grooves 52 a and 54 a are provided in an inner surface 60a of a wall 50 a of the member 46 a, and the groove 58 a is provided inan outer surface 56 a of the member wall 50 a. The grooves 52 a and 54 adefine the zone of deformation 62 a of the member 46 a. The groove 58 ain the member wall outer surface 56 a extends to a depth greater thanhalf the wall 50 a thickness, in a similar fashion to the groove 58 inmember 46.

In this fashion, when an axial force is applied in the direction of thearrows A shown in FIG. 5A, the member 46 a is deformed inwardly, toengage a tube (not shown) located within the deformable member 46 a.This deformation occurs in the same fashion as for the deformable member46 of FIGS. 2A to 3C, forming a circumferential edge 66 a, shown in FIG.5C, for engaging the tube.

The deformable member 46 a has numerous applications in downhole wellassemblies, including as a drilling BOP such as the BOP 20, a wirelinestuffing box such as the stuffing box/coiled tubing injector head 16, avariable venturi such as the internal venturi 32, and as a pipe clamp.Other applications of the member 46 a exist as will readily beunderstood by persons skilled in the art. However, generally speaking,it will be understood that the deformable member 46 a providesanchoring/sealing engagement with a tube located within the hollowmember 46 a when it is moved to the deformed position of FIGS. 5A to 5C.

FIGS. 6A to 7C show a deformable member indicated generally by referencenumeral 46 b, in accordance with a third embodiment of the presentinvention. The deformable member 46 b includes two grooves 52 b and 54 bprovided in an outer surface 56 b of a wall 50 b of the member 46 b,similar to the grooves 52 and 54 in the member 46. The other line ofweakness defines a channel 68, shown more clearly in the enlarged viewof FIG. 6B. The channel 68 has a substantially flat base 70 withinclined side walls, and is provided in an inner surface 60 b of themember wall 50 b. A further circumferential groove 74, substantiallyV-shaped in cross section, similar to the grooves 52,54 and 58 of member46, is provided in the flat base 70 of the channel 68.

When the member 46 b is deformed on application of an axial force A,shown in FIG. 7A, the profile of the channel 68 causes a lip 77, bestshown in FIGS. 7B to 7D, to be formed at a radially outer extreme of themember 46 b, in the region of the deformation zone 62 b. The lip 76 isof an outer diameter greater than the major expansion of the deformablemember 46 b. The lip 76 is relatively soft and deformable, and hasparticular advantages in allowing the member 46 b to be located in anovalised or damaged tube or other bore, as well as providing a sealactivated by a low actuating energy, for use in low pressureenvironments, and/or to provide a gas-tight seal with a tube or bore.This is achieved due to deformation of the lip 76 of the member 46 b oncontact with the tube or bore in which the member is located, when movedto the deformed position of FIGS. 7A to 7D.

The deformable member 46 b has particular applications in downhole wellassemblies as an ECP such as the ECP 42, a bridge plug, such as thebridge plug 24 shown in FIG. 1 (as will be described in more detail withreference to FIGS. 37A to 50E below), as well as a packer such as thepacker 28.

FIGS. 8A to 9C show a deformable member indicated generally by referencenumeral 46 c, in accordance with a fourth embodiment of the presentinvention. The member 46 c is similar to the member 46 b of FIGS. 6A to7D, and includes two grooves 52 c and 54 c provided in an outer surface56 c of a wall 50 c of the member 46 c. Also, a channel 68 c is definedin an inner surface 60 c of the member wall 50 c, similar to the channel68 of FIG. 6A.

The channel 68 c, as shown in FIG. 8B, includes a substantially flatbase 70 c with inclined side walls 72 c. Two circumferentially extendinggrooves 74 c are provided in the flat base 70 c of the channel 68 c, andthe grooves 74 c are connected by a curved portion 78 of the inner wallsurface 60 c.

When the member 46 c is moved to the deformed position, shown in FIGS.9A to 9C, by application of an axial force in the direction A (FIG. 9A),the member 46 c is deformed in the deformation zone 62 c, and the curvedwall portion 78 is deformed outwardly to define a rounded lip 80, bestshown in the enlarged view of FIG. 9B and the perspective view of FIG.9C.

The deformable member 46 c has particular applications similar to thoseof the member 46 b of FIGS. 6A to 7C. However, in addition, the member46 c may be suitable for dynamic applications, such as to provide flowcontrol for a borehole or tubing, similar to the deformable member 46 ofFIGS. 2A to 3C.

FIGS. 10A to 11C show a deformable member indicated generally byreference numeral 46 d, in accordance with a fifth embodiment of thepresent invention. The member 46 d is substantially identical to themember 46 of FIGS. 2A to 3C. However, the member 46 d includes twoupstanding ribs 82 and 84 on an outer surface 56 d of the member 46 d.The ribs 82 and 84 are provided in the region of the deformation zone 62d, and are axially spaced either side of a groove 58 d in an innersurface 60 d of the member wall 50 d, and are inclined towards oneanother. Each rib 82 and 84 is substantially V-shaped in cross-section,such that, when the member 46 d is moved to the deformed position of 56e of the member wall 50 e, and grooves 86 and 88 in an inner surface 60e of the member wall 50 e.

The grooves 86 and 88 are similar to the groove 58 in the member 46 ofFIGS. 2A to 3C and extend into the member wall 50 e to a depth greaterthan half the wall thickness, as shown in particular in the enlargedview of FIG. 12B. An outer portion 90 of the wall 50 e is definedbetween the grooves 86 and 88 in the inner wall surface 60 e. Thegrooves 86 and 88 and the wall portion 90 are such that, when the member46 e is moved to the deformed position shown in FIGS. 13A to 13C, onapplication of an axial force in the direction A (FIG. 13A), the member46 e is deformed in the deformation zones 62 e, and bulges outwardly,such that the wall portion 90 engages a tube in which the member 46 e islocated. This spreads the force exerted on the tube over a greatersurface area, reducing the likelihood of damage to the tube.

Furthermore, the wall portion 90 can be laminated with a sealingmaterial (not shown) such as Nitrile, Viton, or Teflon (trade marks), toprovide a gas-tight seal with the tube, whereby sealing is achieved witha relatively low energizing force. This provides a high-pressure andhigh-temperature sealing capability of the member 46 e. In analternative embodiment the member 46 e is laminated with a relativelysoft metal material (not shown), to provide a metal to metal seal at arelatively low energizing force.

The deformable member 46 e has particular applications as a bridge plug,such as the bridge plug 24 (as will be described below with reference toFIGS. 37A to 50E), as a packer such as the packer 28, a liner hangersuch as the hanger 38, or as an anchor system. Also, the deformablemember 46 e may have dynamic applications such as for providing flowcontrol through borehole or tubing, in a similar fashion to the member46 of FIGS. 2A to 3C.

FIGS. 14A to 15C show a deformable member indicated generally byreference numeral 46 f, in accordance with a seventh embodiment of thepresent invention. The member 46 f is similar to the member 46 e ofFIGS. 12A to 13C. A wall portion 90 f of the member 46 f, shown inparticular in the enlarged view of FIG. 14B, includes a circumferentialgroove 92 which carries a seal, such as a plastics or elastomeric seal,to improve sealing with a tube in which the member 46 f is located, whenmoved to the deformed position of FIGS. 15A to 15C.

FIGS. 16A to 17C shows a deformable member indicated generally byreference numeral 46 g, in accordance with an eighth embodiment of thepresent invention. The member 46 g is similar to the member 46 e ofFIGS. 12A to 13C, and a portion 90 g of member wall 50 g carries aplurality of ridges 94, shown in particular in the enlarged view of FIG.16B. The ridges 94 extend around the circumference of the portion 90 gas shown in FIG. 16C, and are either a simple screw thread, orindividual circumferentially extending ridges.

The deformable member 46 g has general applications as an anchor and/ora seal with multiple point contact with a tube in which the member 46 gis located. The ridges 94 penetrate the tube to fix the member 46 g inposition. The member 46 g has particular applications as a bridge plug,such as the bridge plug 24 (as will be described with reference to FIGS.37A to 50E below), a packer such as the packer 28, a liner hanger suchas the liner hanger 38, or as an anchor system.

FIGS. 18A to 19C show a deformable member indicated generally byreference numeral 46 h, in accordance with a ninth embodiment of thepresent invention. The member 46 h is similar to the member 46 of FIGS.2A to 3C in that it includes two grooves 52 h and 54 h in an outersurface 56 h of a member wall 50 h, and a groove 58 h in an innersurface 60 h of the member wall 50 h. However, the groove 58 h isaxially closer to the groove 52 h than the groove 54 h. This is shown inparticular in the enlarged view of FIG. 18B.

When moved to the deformed position of FIGS. 19A to 19C, this causes themember 46 h to deform in the deformation zone 62 h in the fashion shownin FIG. 19B, nonsymmetrically about groove 58 h. This provides anenergizing load bias under pressure, as will be described in more detailbelow with reference to FIGS. 31 and 32, with greater deformation takingplace in a longer portion 96 of the member 46 h.

The deformable member 46 h has particular applications in the same areaas the deformable member 46 of FIGS. 2A to 3C.

FIGS. 20A to 21D show a deformable member indicated generally byreference numeral 46 i, in accordance with a tenth embodiment of thepresent invention. The member 46 i includes two grooves 52 i and 54 iprovided in an outer surface 56 i of the member wall 50 i, and twogrooves 98 and 100 formed in an inner surface 60 i of the member 50 i.The grooves 52 i, 98,54 i and 100 are provided alternately in the outerand inner wall surfaces 56 i and 60 i respectively, along the length ofthe member 46 i. The grooves 98 and 100 are similar to the groove 58 ofthe member 46 shown in FIGS. 2A to 3C, and extend into the wall 50 i toa depth greater than half the wall thickness. When the member 46 i ismoved to the deformed position of FIGS. 21A to 21D, on application of anaxial force in the direction of the arrows A (FIG. 21A), the memberdeforms in the deformation zone 62 i both inwardly and outwardly, asbest shown in the enlarged view of FIG. 21B.

This forms an outer circumferential edge 66 i for engaging a tube inwhich the member 46 i is located, and an inner circumferential edge 102,for engaging a tube located within the hollow member 46 i.

The member 46 i has particular applications similar to those of themember 46 of FIGS. 2A to 3C and the member 46 a of FIGS. 4A to 5C, incombination.

FIGS. 22A to 23E show a deformable member indicated generally byreference numeral 46 j, in accordance with an eleventh embodiment of thepresent invention. The member 46 j is similar to the member 46 i ofFIGS. 20A to 21D, except that it includes five lines of weakness, withan additional groove 104 provided in an outer surface 56 j of memberwall 50 j. This provides two circumferential edges 106 and 108 in theouter wall surface 56 j when the member 46 j is moved to the deformedposition of FIGS. 23A to 23D. This affords improved contact with a tubein which the member 46 j is located, together with engagement with atube located in the member 46 j, through contact with an edge 102 j inthe inner wall surface 60 j. The deformable member 46 j has applicationssimilar to the member 46 i of FIGS. 20A to 21D, including theabove-noted advantages.

FIGS. 24A to 25C show a deformable member indicated generally byreference numeral 46 k, in accordance with a twelfth embodiment of thepresent invention. The deformable member 46 k operates to move betweendeformed and undeformed positions in a similar fashion to the deformablemembers of FIGS. 2A to 23D, but is of a different structure, as will bedescribed herein.

The deformable member 46 k comprises a body having a first generallyhollow cylindrical portion 110 and a second hollow bulbous portion 112.The hollow cylindrical portion 110 has a member wall 114 of a firstgeneral wall thickness, and the bulbous portion 112 has a wall 116 whichvaries in thickness to a minimum wall thickness at the area 113 wherethe outside diameter of the bulbous portion 112 is greatest.

The difference in the wall thickness between the hollow cylindricalportion 110 and the bulbous portion 112 is shown in particular in theenlarged view of FIG. 24B.

FIGS. 25A to 25C show the deformable member 46 k when it has been movedto the deformed position, on application of an axial force in thedirection of the arrows A, shown in FIG. 25A, in similar fashion to thedeformable members of FIGS. 2A to 23D. Application of the axial forcecompresses the bulbous portion 112, which deforms and “bulges”outwardly, in a similar fashion to the portion of the deformable member46, in the deformation zone 62. This brings an outer surface 118 of thebulbous portion 112 into contact with a tube in which the member 46 k islocated for anchoring and/or sealing engagement therewith.

The rounded nature of the bulbous portion 112 ensures that a soft,rounded contact is obtained between the outer surface 118 and the tube,and provides a progressive, distributed load, ensuring that highstress-concentration nodes do not form in the member 46 k ondeformation. The member 46 k is generally suited to cyclical expansionapplications, and has particular applications in downhole wellassemblies as a dynamic metal to metal seal, such as used inreciprocating pistons or tubing expansion joints; as an interference fitseal using smooth leading edges of the bulbous portion 112 to provide apress-fit into a tube or seal bore; as tool body connections, PBR sealssuch as the PBR 36, or as lubricator quick connect seals; and as anon-penetrating, non-damaging seal for, in particular, plastic coatedtubes or materials suspectable to corrosion cell formation through adamaged passive layer.

FIGS. 26A to 27B show a deformable member indicated generally byreference numeral 461 in accordance with a thirteenth embodiment of thepresent invention. The deformable member 461 is the most structurallysimple form of deformable member according to the present invention. Themember 461 comprises a hollow cylindrical body 481, which is shown inFIGS. 26A and 26B in an undeformed position.

FIGS. 27A to 27C show the deformable member 461 in a deformed position,following application of an axial force in the direction of the arrows Aof FIG. 27A. This causes the wall 501 of the body 481 to deform to forma ring 282 of material, shown in particular in FIG. 27C, upstanding fromthe outer surface 561 of the member 461. In a similar fashion to theabove described embodiments, this provides sealing with a tube or thelike in which the member 461 is located.

FIGS. 28A to 29C show a deformable member indicated generally byreference numeral 46 m, in accordance with a fourteenth embodiment ofthe present invention. The deformable member 46 m operates to movebetween deformed and undeformed positions in a similar fashion to thedeformable members of FIGS. 2A to 23D, but is of a structure similar tothat of the member 46 k shown in FIGS. 24A to 25C.

The deformable member 46 m comprises a body having a first generallyhollow cylindrical portion 110 m and a second hollow portion 112 m. Thehollow cylindrical portion 110 m has a member wall 114 m of a firstgeneral wall thickness, with two circumferentially extending lines ofweakness in the form of generally rectangular section grooves 284 and286, provided in an outer surface 288 of the portion 114 m. The hollowportion 112 m has a wall 116 m which is of a wall thickness less thanthat of the wall 114 m, and thus a portion of the member wall is definedbetween the grooves 284 and 286.

The member wall 114 m defines shoulders 290,292 which both support thehollow portion 112 m, to constrain deformation of the wall 116 m, andallow for transferral of the axial force to the portion 112 m. Also, themember 46 m includes internal seal carrying channels 294 for carryingseals such as an elastomeric O-ring seal, for sealing to a mandrel orthe like carrying the member. As will be discussed in more detail withreference to FIGS. 30 to 32, a chamber 296 is defined between theportions 110 m and 112 m of the member 46 m and the carrying mandrel.This chamber 296 selectively assists in deforming the member 46 m to thedeformed position of FIGS. 29A to 29C.

The member 46 m is shown in FIGS. 29A to 29C in a deformed position, onapplication of an axial force in the direction of the arrows A of FIG.29A, in a similar fashion to the above described embodiments of theinvention. It will be noted that the wall 116 m, on application of theaxial force, deforms and bulges outwardly, to bring an outer surface 118m of the wall 116 m into contact with a tube or the like in which themember 46 m is located. To allow for this deformation, the grooves 284and 286 become closed, as shown in particular in FIG. 29B.

Referring now to FIG. 30, which is a view of the member 46 m in use,shown in the deformed position of FIG. 29A, the member 46 m is shownlocated on a mandrel 298 and is sealed to the mandrel 298 by O-ringrubber seals 300, located in the seal carrying channels 294. In thisposition, the surface 118 m of the portion 116 m has been brought intocontact with an inner surface 302 of a tube such as a casing 304 inwhich the member 46 m is located. As noted above, the member 46 m can bemoved to the deformed position shown on application of an axial force.As shown in FIG. 30, a force F1 can be exerted on sleeve end portions306 and 308 of the member 46 m to move it to the deformed position.

However, the member 46 m may also be moved to the deformed position byfluid pressure, due to the differential piston area of the member 46 min use, as shown and described briefly above. Differential pressureforces are exerted upon the member 46 m due to the pressures P1 and P2of fluid in the annulus 310 above and below the member 46 m.

The differential piston area is the cross-sectional area of the annulus310, and is determined according to the following calculation:π/4(D2²−D1²)where D1 and D2 are, as shown, the outer and inner diameters of themandrel 298 and the casing 304, respectively. From this, we obtain thepressure force f due to the pressure P1, which is equal to pressuretimes area, as:f=P1×π/4(D2² −D1²)It will be understood that the force due to the pressure P2 iscalculated in a similar fashion. The differential piston area maytherefore allow a fluid pressure force to be exerted on the member 46 m,to move it to the deformed position. However, the differential pistonforce may also be utilized in conjunction with application of an axialforce F1 to maintain the member 46 m in the deformed position.

Referring now to FIG. 31, the member 46 m is shown in the deformedposition of FIG. 29A and mounted on a mandrel 312 similar to the mandrel298 of FIG. 30, except including a pressure vent port 314. The pressurevent port 314 provides fluid communication between the chamber 296 andan inner annulus 316 of the mandrel 312. This allows the member 46 m tobe deformed by differential pressure across the member 46 m, between thechamber 296 and the annulus 310. Thus fluid pressure P3 in the annulus316, acting through the port 314, without the need for axial loading F1(or fluid pressure loading P1 or P2) acts to deform the member 46 m,where P3 is greater than the annulus pressure.

However, in the event that an axial load F1 is used to move the member46 m to the deformed position, pressure P3 may be used as a back-upenergizing method, to maintain deformation of the member 46 m.

Referring now to FIG. 32, there is shown a deformable member similar tothe member 46 m, indicated generally by reference numeral 46 n. Thestructure of the member 46 n is identical to that of the member 46 mexcept that only a single seal 300 n is provided, and that a pressurevent port 318 is provided in the wall 114 n of the portion 110 n ofmember 46 n. This provides fluid communication between the annulus 310and the chamber 296 n of the member 46 n and allows the member 46 n tobe deformed by fluid pressure through the annulus 310, and vent 318 tothe chamber 296 n. Of course, it will be understood that in a similarfashion to the embodiment of FIGS. 30 and 31, the member 46 n may bedeformed by application of axial force F1, or by a combination of axialforce F1 and pressure P1.

FIGS. 33A to 34C show a deformable member indicated generally byreference numeral 46 p, in accordance with a fifteenth embodiment of thepresent invention. The deformable member 46 p is similar to the member461 of FIGS. 26A to 27B, in that it includes a generally hollowcylindrical body. However, the member 46 p differs in that end portions320 and 322 of the member 46 p have a wall thickness which is greaterthan a wall thickness of the body 48 p in a deformation zone 62 p of themember. Also, the wall 50 p in the region of the deformation zone 62 pis preformed into a shape which encourages the member 46 p to deformoutwardly, in the fashion shown in FIGS. 34A to 34C.

Also, a deformation aid in the form of a plastics or rubber O-ring isprovided within the body 48 p at a midpoint 326 of the deformation zone62 p. As shown in particular in FIG. 34C, when the member 46 p isdeformed, for example, on application of an axial force A, shown in FIG.34A, the wall 50 p of the body 48 p in the region of the deformationzone 62 p deforms around and compresses the O-ring 324. This forms aring 282 p of material for engaging the wall of a tube or the like inwhich the member 46 p is located. It will therefore be understood thatthe inclusion of the Oring 324 assists in obtaining the desireddeformation of a plain body such as that of the member 46 p.

Referring now to FIGS. 35A and 35B, there are shown deformable membersindicated generally by reference numeral 46 q, acting as anti-extrusionseals to prevent extrusion of a conventional seal 328 in use. The seal328 receives ends 330 of the members 46 q, which abut a radial shoulder332 of the seal 328. The members 46 q are disposed such that respectivegrooves 54 of each member 46 q are located outside the seal 328 adjacentto faces 334 of the seal 328.

As will be understood by persons skilled in the art, the seal 328 is ofthe type conventionally used for obtaining sealing in a tube, such asthe casing 336 shown in FIG. 35B, which is a view of the seal 328 andmembers 46 q in use, with the members 46 q moved to a deformed position.Conventionally, such seals 328 are mounted on mandrels carryinganti-extrusion rings (not shown). However, the seals 328 are of anexpandable plastics or rubber material, which is deformed intoengagement with an inner wall 338 of the casing 336 to provide sealing.As the anti-extrusion rings are not similarly expandable, an annular gap(not shown) exists between the rings and the casing wall 338.Differential pressure across the seal 328 through such an annular gaptends to cause extrusion of the seal 328 and ultimately results in sealfailure.

To overcome this, provision of the members 46 q, and deformation of themembers to the position shown in FIG. 35B, in the fashion describedabove, brings the members into engagement with the casing wall 338,closing the annular gap and protecting the seal 328 from extrusion.

FIGS. 36A and 36B illustrate a collapse aid 340 for a deformable member,in this case, the member 46 of FIGS. 2A to 3C. The collapse aid 340 isprovided to assist in returning the deformable member 46 from thedeformed position shown in FIG. 36A, to the undeformed position of FIG.36B. The collapse aid 340 is in the form of a sleeve, typically known asan extrusion cone, and has a beveled leading edge 342. The collapse aid340 is run downhole to the location of the deformable member 46, and isrun over the member 46 as shown in FIG. 36A. The beveled edge 342 isthen brought into abutment with the member 46 in the deformation zone62, contacting a face 344 of the member 46. This, together withapplication of a tensile load in the direction of the arrows B, assistsin returning the member 46 to the undeformed position.

The provision of the collapse aid 340 is particularly advantageous inthat it avoids the requirement for very high tensile loading to beapplied through the deformation zone 62 of the member 46 to recover themember to the undeformed position. This is particularly useful as incertain situations, the high stress applied to the member 46 duringmovement to the deformed position of FIG. 36A can cause permanentdamage, preventing full retraction to the undeformed position.

As noted above, for each of the deformable members 46 to 46 q describedabove, an alternative fashion of moving the members between deformed andundeformed positions is to provide relative degrees of freedom. Forexample, either end of one of the members may be fixed relative to, forexample, a carrying mandrel, in particular to limit the effect ofdifferential pressure forces due to the differential piston areaencountered, as described above with reference to FIGS. 30 to 32 inparticular. In such situations, where relatively high pressures areencountered, it may not be desirable to load the members to the fullextent of the potential differential piston loading, as this may exceedthe design capabilities of the material of the members, and causefailure.

Restraining one end of the members from movement towards the oppositeend ensures that differential piston loading applied from theconstrained end does not further energize the seal, preventing furtherdeformation and seal failure under extreme pressure.

Referring now to FIGS. 37A to 47B, there are shown various views of abridge plug indicated generally by reference numeral 120, in accordancewith a first embodiment of the present invention, and including thedeformable member 46 of FIGS. 2A–3C. However, it will be appreciated bypersons skilled in the art that the bridge plug 120 may equally includea deformable member in accordance with any of the second to twelfth andfurther embodiments of the present invention described above withreference to FIGS. 4A–25C; 33A–34B; and 51A–54B below.

Turning initially to FIGS. 37A and 37B, there are shown longitudinallysectioned perspective and longitudinal sectional views, respectively, ofthe bridge plug 120, shown in a running position where the deformablemember 46 is in the undeformed position of FIGS. 2A to 2C.

A bridge plug is generally used in downhole situations where, forexample, pressure isolation and testing is required or a casing orlining installed in a borehole has become corroded, perforated orotherwise damaged, allowing ingress of non-well fluids, sand and othermaterials detrimental to the retrieval of well fluids through theborehole. The bridge plug isolates the damaged portion of the casing,and allows fluid communication from a location below the bridge plug toabove the bridge plug, allowing well production to continue andpermitting the access of well tools into the borehole, whilst isolatingthe non-well fluids, sand and the like from the remainder of the casing.Bridge plugs are typically run into a borehole as part of a tool string,to a depth where the bridge plug is required to be located or “set” inthe casing.

The bridge plug 120 of FIGS. 37A and 37B is run-into a borehole as partof such a tool string, and includes a setting tool (not shown), coupledto the bridge plug 120 at an end 122, which is the upper end of thebridge plug in use, when run into the borehole. The bridge plug 120generally comprises the upper end 122, which includes a “fish neck”profile 124, to allow retrieval of the tool, a ratchet mechanism 126, aseal 46 in the form of the deformable member, a slip mechanism 128 andan end 130 which forms the lower end of the bridge plug 120 when it isrun into the borehole, and which includes a set/unset profile 132. Thebridge plug 120 is shown in FIG. 37B in the upright position in which itis run into the borehole. Each of the separate components of the bridgeplug 120 will be described in more detail with reference to FIGS. 38A to47B below.

FIGS. 38A and 38B are enlarged views of the bridge plug 120 showing theupper and lower parts of the plug, respectively.

The upper end 122 of the bridge plug 120 comprises a tubular fish-necksleeve 134, coupled to the ratchet mechanism 126 by a transfer sleeve136, which is secured to the fish-neck sleeve 134 by a threadedconnection 137, secured using locking screws 138. The transfer sleeve136 is coupled to the ratchet mechanism 126 via shear screws, two ofwhich are shown and given the reference numeral 140. The ratchetmechanism 126 will be described in more detail with reference to FIGS.39A and 39B below. However, the ratchet mechanism 126 is connected tothe seal 46, and both the ratchet mechanism 126 and the seal 46 aremounted on an inner sleeve 142 of the bridge plug 120, which extends tothe end 130 and carries the set/unset profile 132. The slip mechanism128 is mounted on the inner sleeve 142 below the seal 46, and the seal46 is coupled to part of the slip mechanism 128. The slip mechanism 128will be described in more detail with reference to FIGS. 41A and 41Bbelow.

Turning now to FIGS. 39A and 39B, there are shown enlarged views of theratchet mechanism 126, and perspective views of segments of the ratchetmechanism, respectively. The ratchet mechanism 126 includes an uppersleeve 144, coupled to the transfer sleeve 136 by the shear screws 140;a release sleeve 146, coupled also to the transfer sleeve 136 by athreaded connection 147, secured using locking screws 148 (one shown); aratchet segment 150 carrying ratchet teeth 152 for engagingcorresponding teeth on the inner sleeve 142; and a shaped ratchetreverse segment 154. A number of ratchet segments 150 and ratchetreverse segments 154 are provided spaced around the bridge plug 120,although only two are shown in the drawings. FIG. 39B shows a ratchetsegment 150 and a ratchet reverse segment 154 in more detail. It will beseen that the ratchet segment 150 is generally arcuate, and has a curvedface 156 for co-operating with a corresponding curved face 158 of theratchet reverse segment 154. As will be described in more detail below,co-operation between the ratchet teeth 152 on the ratchet segment 150and the corresponding teeth on the inner sleeve 142 acts to restrainmovement of the bridge plug when it is moved to a set position and theseal 46 is deformed. The ratchet segments 150 are normally retained inengagement with the inner sleeve ratchet teeth by a shoulder 202 ofrelease sleeve 146.

FIG. 40 is an enlarged view of the seal 46, and it will be noted thatthe seal 46 similar to the deformable member shown in FIG. 2A anddescribed above. However, the seal body 48 includes shoulders 160 and162 at either end of the body, the end 160 carrying an elastomericO-ring seal 164 for sealing an upper end of the seal 46 to the innersleeve 142. A lower end of the seal 46 remains unsealed with the innersleeve 142, to allow pressure equalization between an annular cavity 204and the remainder of the plug 120.

Referring now to FIGS. 41A and 41B, there are shown exploded perspectiveand perspective views, respectively, of the slip mechanism 128. The slipmechanism 128 includes a dynamic slip mandrel 166, a static slip mandrel168, and a number of slips 170, only one of which is shown in FIG. 41A.The slip mechanism is of a type known in the art, each of the dynamicand static slip mandrels 166 and 168 including a plurality of segments172 disposed around the mandrels. Adjacent pairs of segments 172together define uplift ramps 174 and collapse ramps 176. Each slip 170includes an arcuate body portion 178 carrying slip teeth 180, withgenerally T-shaped segments 182 formed at either end of the body portion178. The body portion 170 defines uplift ramps 184 and the T-shapedsegments define collapse ramps 186. When the slip mechanism 128 isassembled, as shown in FIG. 41B, uplift ramps 174 abut the correspondinguplift ramps 184 of the slips 170, and the collapse ramps 176 of themandrels 166 and 168 abut the corresponding collapse ramps 186 of theslips 170. This allows the slips to be moved radially outwardly toengage a casing wall in which the bridge plug 120 is located, as will bedescribed in more detail below.

Referring now to FIG. 42, there is shown an enlarged view of the end 130of the bridge plug 120. The set/unset profile 132 includes a connectionthread 188 which serves for connecting the bridge plug 120 to part ofthe setting tool, and an elastomeric O-ring seal (not shown) located ina groove 190. In addition, the end 130 carries an internal radiallybridge plug 120 to be compressed to set the plug; and a no-go shoulder196 to allow the bridge plug 120 to be axially extended for un-settingthe plug.

There follows a description of the method of setting and un-setting thebridge plug 120. The plug 120 is held in the extended, unset position ofFIGS. 37A and 37B by restraining the plug 120 between the fish-neck 124and the set/unset profile 132. Co-operation between the collapse ramps176 of the mandrel segments 172 and the collapse ramps 186 of the slips170 ensures that the slips 170 are fully retracted. This allows thebridge plug 120 to be run into the borehole casing in the runningposition of FIGS. 37A and 37B.

When the bridge plug 120 has been located at a desired depth in theborehole casing, the setting tool (not shown) is initiated. The settingtool axially compresses the bridge plug 120 between fish-neck 124 andset/unset profile 132, moving the fish-neck sleeve 134 downwards. Thisdownward movement is transferred to the dynamic slip mandrel 166 of theslip mechanism 128 through the transfer sleeve 136, ratchet mechanism126 and the seal 46, which initially remains in the undeformed positionof FIGS. 37A and 37B. Downward movement of the dynamic slip mandrel 166towards the static slip mandrel 168 forces the slips 170 up the upliftramps 174 of the mandrels. This moves the slips 170 radially outwardly,by co-operation with the slip uplift ramps 184, until they are fullyengaged in the casing wall and cannot expand further.

Once the dynamic slip mandrel 166 has ceased to move axially,compressive axial loading on the bridge plug 120 is transferred to theseal 46. A predetermined load is applied which fully energizes the seal46 to move it to the deformed position, where it expands into contactwith the casing wall, as described above. The bridge plug is thereforenow in the position shown in FIGS. 43A and 43B, with the seal 46 andslips 170 fully expanded, as shown in FIG. 44 and FIGS. 45A and 45B,respectively.

As the seal 46 is axially compressed, its axial travel is secured andlocked by the ratchet mechanism 126, by cooperation between the ratchetteeth 152 of the ratchet segment 150 and the corresponding teeth on theinner sleeve 142. This ensures that the load applied to both the seal 46and the slips 170 is retained, and securely holds the bridge plug 120 inthe casing in the set position shown in FIGS. 43A and 43B.

Having knowledge of the compressive load required to move the bridgeplug 120 to the set position allows a predetermined shear-rated ring orrelease mechanism (not shown) on the setting tool to disengage from theshoulder 192 of the set/unset profile 132. This ensures that the settingtool automatically releases from the bridge plug 120 when sufficientforce has been applied to set the plug, and ensures that the settingtool cannot apply a load too great for the plug 120, which wouldotherwise cause damage. When the shear-ring has released the settingtool from the bridge plug 120, the setting tool is withdrawn andretrieved to surface. Pressure loading on the bridge plug 120 from aboveor below acts to further compress and engage both the slip mechanism 128and the seal 46 with the casing wall, to further enhance pressureretaining performance of the bridge plug 120.

Referring now to FIGS. 46A and 47A, the bridge plug 120 is shown afterhaving been returned from the set position of FIGS. 43A and 43B, toallow retrieval of the bridge plug 120 after it has carried out therequired well operation.

The bridge plug 120 is retrieved from the set position of FIGS. 43A and43B by coupling a retrieval tool (not shown) to the bridge plug 120 andlatching it to the fish-neck profile 124. The retrieval tool generates aforce which extends the bridge plug 120 between the fish-neck profile124 and the set/unset profile 132. It is important to note that thebridge plug 120 is extended from the set position independently of theslips 170. The bridge plug 120 is therefore not dependent uponengagement of the slips 170 with the casing wall to allow retrieval.

Extending the plug 120 shears the shear screws 140 into parts 198 and200, allowing axial movement of the transfer sleeve 136 relative to theupper sleeve 144 of the ratchet mechanism 126, carrying the ratchetrelease sleeve 146 therewith.

Axial movement of the release sleeve 146 de-supports the ratchetsegments 150, which are normally restrained from radial movement by theshoulder 202 of the release sleeve 146 and the shaped ratchet reversesegments 154. When the ratchet segments 150 are de-supported, as shownin the enlarged view of FIG. 46B, the ratchet segments 150 and theratchet reverse segments 154 move radially outwardly, such that theratchet teeth 152 disengage from the corresponding teeth on the innersleeve 142. This allows the shoulder 160 of the seal 46 to move axiallytowards the fish-neck sleeve 134, to move the seal 46 to the undeformedposition.

Further axial extension of the bridge plug 120 releases the slips 170from the casing wall, by an interaction between the collapse ramps 176of the mandrels 166,168, and the collapse ramps 186 of the slips 170.Full extension of the bridge plug 120 to the position shown in FIG. 46Acauses full retraction of the seal 46 and slips 170. The bridge plug 120may then be retrieved to surface.

Referring now to FIGS. 48A and 48B, there are shown longitudinallysectioned perspective and longitudinal sectional views, respectively, ofa bridge plug indicated generally by reference numeral 120 a, inaccordance with a second embodiment of the present invention. Likecomponents of the bridge plug 120 a with the bridge plug 120 of FIG. 37Ashare the same reference numerals, with the addition of the letter “a”.The bridge plug 120 a includes a seal 46 a, similar to the deformablemember 46 of FIGS. 2A to 3C and the bridge plug 120 a is shown in FIGS.48A and 48B in a running position, similar to that of the bridge plug120 shown in FIGS. 37A and 37B.

The bridge plug 120 a is shown in more detail in the enlarged views ofthe upper and lower portions of the bridge plug shown in FIGS. 48C and48D. The plug generally comprises an upper end 122 a with fish-neckprofile 124 a, a locking key mechanism 206 (shown in FIGS. 49A and 49Band described below), a slip mechanism 128 a (shown in FIG. 49C), theseal 46 a, a retractable ratchet mechanism 208 (shown in more detail inFIGS. 49D, 50B and 50C and described below), a transfer key mechanism210 (shown in FIGS. 49E, 50D and 50E and described below), and a lowerend 130 a, for coupling to a shear-ring mechanism of a setting tool. Thebridge plug 120 a is run into the casing of the borehole on a settingtool, in a similar fashion to the bridge plug 120 of FIG. 37A.

Referring now to FIGS. 49A to 50E, there are shown enlarged andperspective views of the locking key mechanism 206; and perspectiveviews of the slip mechanism 128 a, retractable ratchet mechanism 208 andtransfer key mechanism 210, respectively.

Turning initially to FIGS. 49A and 49B, the locking key mechanism 206allows the bridge plug 120 a to be returned to an unset position afterhaving been set, as will be described below. The key mechanism 206includes a release sleeve formed by the outer sleeve 218, and releasekeys 222 (two shown) located in apertures 224 of an inner sleeve 226 ofthe key mechanism 206. Each release key 222 defines an internal shoulder228 which engages in a recess 230 of inner plug sleeve 216, to restrainthe plug 120 a in a set position, as will be described below. A radiallyinner shoulder 232 of the outer sleeve 218 normally retains the releasekeys 222 in the apertures 234, such that the key shoulder 228 abuts aface 234 of the recess 230, to restrain the inner sleeve 226 relative tothe inner plug sleeve 216.

The slip mechanism 128 a shown in FIGS. 48C and 49C differs from themechanism 128 of bridge plug 120 in that it includes a slip lockingratchet 212 having a ratchet segment 214, which carries internal ratchetteeth, for engaging corresponding teeth on the inner sleeve 216 of thebridge plug 120 a. The ratchet segment 214 is carried by the dynamicslip mandrel 168 a and retains the slips 170 a when the bridge plug 120a is moved to the set position, as will be described below. The mandrel166 a is initially static, and is coupled to the locking key mechanism206 as described above. Both the inner and outer sleeves 126,128 arecoupled to the fish-neck sleeve by screws 220 (one shown).

The slip mechanism 128 a and the seal 46 a are carried on the innersleeve 216 of the bridge plug 120 a, and the inner sleeve 216 is coupledto the retractable ratchet mechanism 208 as shown in FIG. 49D.

The ratchet mechanism 208 includes a ratchet release sleeve 236, coupledto the inner sleeve 216 of the plug by offset shear screws (not shown).The release sleeve 236 carries elastomeric O-ring seals 237 for sealingthe release sleeve 236 to the inner sleeve 216. Inner retractableratchet segments 238 (two shown) of the ratchet mechanism 208 carryratchet teeth on their outer surfaces, and outer ratchet segments 240carry inner ratchet teeth for engaging the corresponding teeth on theratchet segments 238.

The inner ratchet segments 238 are disposed in ratchet housing apertures242 in the inner sleeve 216, and are supported by the release sleeve236, to retain the segments 238 in the position shown in FIG. 49D whenthe bridge plug 120 a is being run and set. The outer ratchet segments240 are disposed in ratchet housing apertures 244 in an outer sleeve 246of the bridge plug 120 a. The inner and outer ratchet segments 238 and240 are shown in more detail in FIGS. 50B and 50C and described below.

The transfer key mechanism 210 shown in FIG. 49E allows movement of theinner plug sleeve 216 relative to the outer sleeve 246, for moving thebridge plug 120 a, between set and unset position. The transfer keymechanism 210 is shown in more detail in FIGS. 50D and 50E. However, thetransfer key mechanism 210 generally comprises a transfer sleeve 248which includes a number of recesses 250 (two shown) for retaining anumber of shaped transfer keys 252.

As shown, outer portions of the transfer keys 252 engage in recesses 254formed in the outer sleeve 246 of the plug 120 a. This restrains thetransfer sleeve 248 relative to the outer sleeve 246, for movementtherewith.

Turning now to FIG. 50A, there is shown part of the bridge plug 120 a ofFIG. 48B, with the seal 46 a, outer sleeve 246, and part of the transferkey mechanism 210 removed for clarity.

FIGS. 50B and 50C illustrate the retractable ratchet mechanism 208 inmore detail, with the outer sleeve 246 removed as shown in FIG. 50A.Each inner retractable ratchet segment 238 is generally I-shaped and iscurved, end portions 256 and 258 of each segment 238 carrying angledcollapse ramps 260. These collapse ramps 260 engage with correspondingcollapse ramps (not shown) carried on shoulders 262 in the inner sleeve216, which extend into the ratchet housing apertures 242. This causeseach retractable ratchet segment 238 to be urged radially inwardly bythe inner sleeve 216, when the bridge plug is compressed.

However, as shown in FIG. 50C, each retractable ratchet segment 238 issupported by the release sleeve 236 when the bridge plug 120 a is runinto the borehole casing. This prevents the movement of the segments 238radially inwardly.

The outer ratchet segments 240 include pocket springs (not shown),located in chambers 264 in each of the segments 240, which urge thesegments 240 in the direction of the arrow B (FIG. 50B), by actingagainst a wall of the outer sleeve 246 defining the ratchet housingapertures 244. As will be described below, when the inner sleeve 216 ismoved downwards, this urges the ratchet segments 238 and 240 intoengagement.

FIGS. 50D and 50E show the transfer key mechanism 210 with the outersleeve 246 removed, for clarity. The transfer sleeve 248 carrieselastomeric O-ring seals 249, for sealing transfer sleeve 248 to theinner sleeve 216.

Each transfer key 252 includes keyways 264 for slidably engagingretaining tracks 266 extending into apertures 268 in the inner sleeve216, through which the transfer keys 252 extend. This allows the innersleeve 216 to move axially with respect to the transfer sleeve 248 andthe outer sleeve 246, which are coupled by the transfer keys 252, asnoted above.

There follows a description of the method of setting the bridge plug 120a of FIGS. 48A to 50E. The bridge plug 120 a is run into a boreholecasing in the unset position of FIG. 48A. When the bridge plug 120 a hasbeen located at the desired depth, the setting tool is initiated, whichsecures the fish-neck sleeve 134 a relative to either the casing wall,or to an end 270 of the transfer sleeve 248.

An axial compressive force is then applied to the bridge plug 120 a bythe setting tool to compress the plug between the fish-neck sleeve 134and the end 270 of the transfer sleeve 248. This causes relative upwardmovement of the transfer sleeve 248 towards the fish-neck sleeve 234. Toapply the compressive load upon the bridge plug 120 a, the setting tooleither anchors the fish-neck sleeve 134 a to the casing wall (as notedabove), to allow upward jarring action to apply a load on the end 270 ofthe transfer sleeve 248; or anchors the fish-neck sleeve 134 a relativeto the end 270 of the transfer sleeve 248 (as noted above), and thecompressive load is then generated within the setting tool to compressthe bridge plug between the end 270 and the fish-neck sleeve 134 a.

Upward movement of the transfer sleeve 248 is transferred to the outersleeve 246 by the transfer keys 252, and the transfer sleeve 248 and theouter sleeve 246 move upwardly relative to the inner sleeve 216, towardsthe fish-neck sleeve 134 a.

Movement of the outer sleeve 246 in this way moves the outer ratchetsegments 240 of ratchet mechanism 208 also axially upwardly over theinner retractable ratchet segments 238. Cam faces 272 and 274 (FIG. 48D)between the outer sleeve 246 and the outer ratchet segments 240, and theouter sleeve 218 and the outer ratchet segments 240, respectively, forcethe segments 240 radially inwardly such that ratchet teeth of thesegments 238 and 240 engage. This locks and retains axial movement ofthe transfer sleeve 248 and outer sleeve 246.

The axial upward movement is transferred through the seal 46 a, whichinitially remains in the undeformed position, to the dynamic slipmandrel 166 a, through the shoulder 160 of the seal 46 a. This causesthe dynamic slip mandrel 166 a to move axially upwardly towards thefish-neck sleeve 134 a, axial travel of the mandrel 166 a being retainedby the ratchet segments 214 of the slip locking ratchet 212. This forcesthe slips 170 a out into engagement with the casing wall, in a similarfashion to the slips 170 of bridge plug 120. The slips 170 a are lockedby the ratchet 212 securing the dynamic slip mandrel 166 a once it hasceased to move axially, and retaining the slips 170 a in engagement withthe casing wall. Further applied axial loading on the bridge plug 120 ais then transferred to the seal 46 a, and a predetermined loading movesthe seal to the deformed position and into contact with the casing wall.The seal 46 a is retained in the deformed position by the retractableratchet mechanism 208.

In a similar fashion to the bridge plug 120, knowledge of thecompressive load required to activate the bridge plug 120 a allows apredetermined shear-rated ring (not shown) on the setting tool orrelease mechanism to disengage from the bridge plug. Once the shear ringhas completed its function, the setting tool is withdrawn and retrievedto surface. The bridge plug 120 a is now set in the casing and pressurefrom above or below further compresses the bridge plug to furtherenergize both the slip mechanism 120 a and the seal 46 a, enhancingpressure retaining performance.

Un-setting of the bridge plug 120 a for retrieval is achieved in thefollowing fashion. A retrieval tool (not shown) is run into the boreholeand into the bridge plug 122 a, to exert a downward loading on an upperend 273 of the ratchet release sleeve 236. This shears the shear screwscoupling the release sleeve 236 to the inner sleeve 216 and moves theratchet release sleeve 236 downwardly. When the sleeve 236 has beenmoved downwardly a sufficient distance, the retractable ratchet segments238 are no longer supported. Interaction between the collapse ramps 260of the segments 238 and the corresponding collapse ramps in the sleeve216 forces the segments 238 radially inwardly towards a bore 278 of theplug. The segments 238 are therefore moved out of engagement with theouter ratchet segments 240. Radial profiling of the retractable ratchetsegments 238 prevents then from falling into the bore 278, and as shownin FIG. 50B, the outer ratchet segments 240 are shaped to be preventedfrom falling through the ratchet housing apertures 242 for the segments238, by the shoulders 262. The ratchet mechanism 208 has therefore nowbeen disengaged.

Further downward movement of the ratchet release sleeve 236 brings itinto contact with the transfer sleeve 248, and continued downwardmovement acts to extend the seal 46 a, by moving the transfer sleeve 248downward. This is achieved by the interaction between the sleeves 248and 246 through the transfer keys 252.

The slip mechanism 128 a differs from the slip mechanism 128 of plug 120in that it remains in full contact with the casing wall throughout theprocess up to extension of the seal 46 a to the undeformed position.Indeed, this allows the downward load to be imparted upon the ratchetrelease sleeve 236 relative to the casing (downward jarring).

The retrieval tool is now latched into the fish-neck sleeve 134 a, toallow the bridge plug 120 a to be jarred upwardly. This shears shearscrews 280 by which the outer sleeve 218 is coupled to the inner sleeve226 of the locking key mechanism 206, allowing upward movement of thesleeve 218. This moves the inner shoulder 232 of the sleeve 218 axiallyupwardly, de-supporting the release keys 222. When the release keys 222are de-supported, this allows movement of the previously static slipmandrel 168 a, which in turn retracts the slips 170 a from the casingwall.

The bridge plug 120 a can then be fully extended with full retraction ofboth the seal 46 a and the slip mechanism 128 a, and the plug 120 a canbe retrieved to surface.

It will be appreciated that references herein to upward and downwardmovement are relative to the location of the bridge plugs 120 and 120 ain a borehole casing, and, by way of example, the bridge plugs have beendescribed as if located in a substantially vertical portion of aborehole.

Turning now to FIGS. 51A to 52B, there is shown a deformable memberindicated generally by reference numeral 46 r, in accordance with afurther embodiment of the present invention. The member 46 r isessentially similar to the members 46 to 46 q described above. FIGS. 51Aand 51B show the member 46 r in an undeformed position, whilst FIGS. 52Aand 52B show the member in a deformed position. The member 46 r includesthree lines of weakness 52 r, 54 r and 58 r defined by rings of materialof the member body 50 r. These lines of weakness are formed by changesin the geometry of the body 50 r, and define three circumferentialnodes, which form weak points in the body 50 r under load. The body 50 ris shaped such that the line 50 r is over-center with respect to theremainder of the body 50 r, and this ensures that when a load is appliedto the member 46 r, the member deforms outwardly into the position shownin FIGS. 52A and 52B, to sealingly engage a tube in which the member 46r is located.

FIGS. 53A to 54B are views of a deformable member indicated generally byreference numeral 46 s, in accordance with a still further alternativeembodiment of the present invention. The member 46 s is essentiallysimilar to the member 46 r of FIGS. 51A to 52B, but includes four linesof weakness 52 s, 54 s, 58 s and 58′s. The body 50 s of the member 46 sis shaped such that a circumferential seal carrying channel 59 s isformed in the outer surface 56 s of the body 50 s, between the lines ofweakness 58 s and 58′s. This allows an elastomeric or similar seal to becarried in the channel 59 s.

Referring now to FIG. 55, there is shown a graph of the axial loadapplied to a test deformable member (y axis), against the resultantdeformation of the member (x axis). The member 46 s (shown in FIGS. 53Ato 54B) in particular was tested. Point “a” is the load point at whichplastic deformation of the member (to the deformed position) begins tooccur. Load point “b” is the point at which the member is fully deformedinto contact with a tube or cylinder. Loading the member beyond loadpoint b causes no further plastic deformation until load point “c” isreached, when secondary plastic deformation is initiated. Between loadpoint c and load point “d”, the member deformation zone is compressed,and when load point d is reached, the member is permanently plasticallydeformed, and relatively no further deformation occurs beyond point d(indicated by “e”). The ideal operating range of the member is from zeroload up to load point b; however, the member can provide recoverabledeformation up to load point c. It will be understood that all of theabove described members 46 to 46 r of the present invention, when loadedin a similar fashion to the member 46 s, behave in this fashion.Accordingly, the graph of FIG. 55 generally applies to all embodiments.

It will further be understood that such secondary deformation isgenerally undesired. There are three main ways in which secondarydeformation can be avoided:

Firstly, by limiting the load. This can be achieved by utilizing ashear/release mechanism with a predetermined load rating which, duringcompression of the member, prevents inadvertent overloading of themember. This requires prior knowledge of the load at which secondarydeformation will initiate.

Secondly, by limiting travel. Limiting the travel allowed during thecompression sequence will prevent secondary deformation. This requiresprior knowledge of the expected reduction in length of the member withinthe primary deformation range, that is, the point at which secondarydeformation will occur must be known.

Thirdly, by providing a deformation aid. Introduction of a supportmaterial (either internally or externally) will reduce the tendency forthe member to deform and will increase the load at which secondarydeformation will occur, thus increasing the operation envelope of themember. A deformation aid is described above (FIGS. 33A to 34B), but ashaped metal insert could equally be used.

Reference herein to the deformable members being initially rigid are tothe members being sufficiently rigid such that the members remain in theundeformed position until a determined axial force is applied to themember, to deform the member about the lines of weakness, as describedabove.

Various modifications may be made to the foregoing within the scope ofthe present invention.

The deformable members described above may equally be used in any tubeor bore other than a borehole of a well of well tubing, such as, forexample, surface gas, oil or other fluid pipelines. The deformablemembers described above are generally moved between deformed andundeformed positions. However, the deformable members may be initiallypartially deformed or preformed, such as the deformable member of FIGS.24A to 25C, and may be moveable between the partially deformed orpreformed position and a further deformed position. The deformablemembers may be of any suitable material which allows deformation to takeplace as described above. The deformable members may be deformed by anaxial pressure force, generated, for example, by fluid pressure in atube or bore in which the deformable is located.

The deformable members may be multiply reusable, or may be only oncedeformable, for example, for use in a “one-shot” operation. The collapseaid 340 may be provided as part of a tool carrying the deformablemember. It will be understood that it is the location of the lines ofweakness in the deformable member which is of primary importance, butthat the depth of the, for example, grooves, is also significant indetermining the direction of deformation.

1. An initially rigid deformable member for use as a seal or anchor,said deformable member having a generally hollow cylindrical bodydefining a cylinder wall having a wall thickness and a line of weaknesson one surface of the body which permits the cylinder wall to deform inresponse to an applied force, to form a ring of material around thecireumference of the cylindrical body, the ring being generallyupstanding from the surface of the cylinder wall, the surface beingopposite the surface upon which the line of weakness exists.
 2. Adeformable member as claimed in claim 1, wherein the ring of material isformed on the outer surface of the cylinder wall.
 3. A deformable memberas claimed in claim 1, wherein the ring of material is formed on theinner surface of the cylinder wall.
 4. A deformable member as claimed inclaim 1, wherein the member is deformable on application of an axialforce at an end of the cylinder.
 5. A deformable member as claimed inclaim 1, wherein the member is deformable on application of a radialtree.
 6. An initially rigid definable member comprising: a body having afirst, generally hollow cylindrical body portion of a first general wallthickness, and a second, hollow bulbous deformable body portion,extending inwardly to engage tubing located within the deformable memberat least part of the second, deformable body portion being of a wallthickness less than said first wall thickness of the first body portion,the second, deformable body portion being deformable in response to anapplied force, in a direction transverse to a main axis of the body, toallow the member to deform.
 7. A deformable member as claimed in claim6, wherein the second, hollow bulbous deformable body portion has amaximum outside diameter greater than that of the first, generallyhollow cylindrical body portion and extends outwardly to engage tubingin which the member is located.
 8. A deformable member as claimed inclaim 6, wherein the second hollow bulbous deformable body portionextends inwardly to engage tubing located within the deformable member.9. An initially rigid deformable member comprising: a body having afirst, generally hollow cylindrical body portion of a first general wallthickness, and a second, hollow deformable body portion, at least partof the second, deformable body portion being of a wall thickness lessthan said first wall thickness of the first body portion, the second,deformable body portion being deformable in response to an appliedforce, in a direction transverse to a main axis of the body, to allowthe member to deform.
 10. A deformable member as claimed in claim 9,wherein the first, generally hollow body portion includes a first partof the wall of the member body, and defines circumferentially extendingshoulders for supporting and transferring force to the second, hollowdeformable body portion.
 11. A well tool comprising: an initially rigiddeformable member comprising: a body having a first, generally hollowcylindrical body portion of a first general wall thickness, and asecond, hollow deformable body portion, at least part of the second,deformable body portion being of a wall thickness less than said firstwall thickness of the first body portion, the second, deformable bodyportion being deformable in response to an applied force, in a directiontransverse to a main axis of the body, to allow the member to deform.12. An initially rigid deformable member comprising: a generally hollowcylindrical body defining a member wall, the wall having at least threecircumferential lines of weakness therein, said lines of weakness beingspaced along a main axis of the body, the axially outermost lines ofweakness defining a zone of deformation of the body, wherein the memberis deformable in the deformation zone in response to an applied force,in a direction transverse to said body main axis, said directiondetermined by the location of the other one of said lines of weakness inthe wall, said other one of said lines of weakness in the wall beingbetween said lines of weakness that define the zone of deformation. 13.An initially rigid deformable member comprising: a generally hollowcylindrical body defining a member wall, the wall having at least threecircumferential lines of weakness therein, the lines of weaknesscomprising circumferentially extending rings of material forming part ofthe member body said lines of weakness being spaced along a main axis ofthe body, the axially outermost lines of weakness defining a zone ofdeformation of the body, wherein the member is deformable in thedeformation zone in response to an applied force, in a directiontransverse to said body main axis, said direction determined by thelocation of the other one of said lines of weakness in the wall, andwherein the member deforms by folding about the rings.
 14. An initiallyrigid deformable member comprising: a generally hollow cylindrical bodydefining a member wall, the wall having at least three circumferentiallines of weakness therein, each line of weakness comprisingcircumferentially extending rings of material forming part of the memberbody, said circumferentially extending rings of material being spacedalong a main axis of the body, the axially outermost circumferentiallyextending rings of material defining a zone of deformation of the body,wherein the member is deformable in the deformation zone by foldingabout said rings, the member being deformable in response to a forceapplied in a direction transverse to said body main axis, said directiondetermined by the location of the other one of said circumferentiallyextending rings of material.